In the field of printing such as newspaper printing and magazine printing, image data produced through editing operation is subjected to RIP (Raster-Image-Processing) to generate binary data, and the binary data is recorded on a plate made of aluminum, thereby forming a plate for printing (printing plate). In forming the printing plate, a CTP (Computer-To-Plate) system for drawing an image directly on a plate without using a film or the like has been recently employed. In this CTP system, a CTP plate (hereinafter referred to simply as “plate”) coated with a photosensitizer is used as a plate, and a modulated laser beam is irradiated on the surface of the plate according to the binary data, thereby forming the printing plate.
Incidentally, when images are drawn on plates of various sizes or when images are consecutively drawn on a large number of plates, for example, the above-mentioned printing plate forming device is preferably structured such that multiple cassettes for accommodating plates are installed and necessary plates are automatically supplied therefrom to the printing plate forming device. In this case, however, it is necessary to install multiple supply devices for supplying the cassettes and to connect them to the printing plate forming device. This causes such problems that a large installation area is required and the structure of the device is complicated.
Therefore, as disclosed in Patent Document 1, there has been proposed a plate supply device including: a multiple cassette unit which has multiple cassettes disposed in multiple stages and which selects, from among them, and delivers a cassette for storing plates necessary for forming a printing plate; and an auto loader unit which receives the delivered cassette, ejects the plates one by one from the received cassette, and supplies them to a printing plate forming device.
Further, Patent Document 2 discloses a plate supply device including: a plate handler which has multiple cassettes disposed in multiple stages and includes an elevator mechanism for allowing the cassettes to independently ascend or descend; and a picker which horizontally moves between the plate handler and an imaging engine, ejects plates from the cassettes, and supplies them to the imaging engine. This plate supply device is structured such that a part of the cassettes are allowed to ascend to thereby form a space in an upper portion of a cassette for storing necessary plates, and then the picker is moved horizontally into the space and positioned in the upper portion of the cassette, thereby ejecting the plates.
According to these plate supply devices, plates can be supplied from multiple cassettes simply by installing a single supply device. This enables downsizing of the device and simplification of the structure of the device.    [Patent Document 1] Japanese Patent No. 3569157    [Patent Document 2] Japanese Patent No. 2825805